1. Field of the Invention:
The invention relates to the field of digitizing waveforms for subsequent digital processing and, in particular, for metal oxide semiconductor (MOS) circuits.
2. Art Background:
It is quite common for integrated circuits to convert a dynamic waveform into digital form for subsequent digital processing. The dynamic waveform is translated into strings of ones and zeros according the shape of the waveform. The most common method for digitizing a dynamic waveform is to sample the waveform using a reference clock whose period is T.sub.r which is much shorter than the period of the waveform, T.sub.w.
The resolution achievable with the prior art method of digitizing waveforms is equal to the reference clock period T.sub.r. In complementary metal oxide semiconductor (CMOS) technology, as in any other semiconductor technology, a certain limit on the highest practical clock frequency exists in any generation of the technology. Thus, the clock frequency cannot be increased without limit in order to improve the resolution of the digitized waveform. Therefore, the resolution achievable with the prior art method is limited to the shortest practical reference clock period T.sub.r in that generation of CMOS technology. In practice, the prior art methods of digitizing a waveform is only practical for a waveform which has very infrequent transitions--transitions that are separated by intervals that are many times greater than T.sub.r. As such, the prior art method of digitizing a waveform is not workable for a waveform whose transitions are separated by intervals approaching the reference clock period T.sub.r. For dynamic waveforms whose transitions are separated by periods less than the reference clock period T.sub.r, the prior art method is non-functional.
It is an object of the present invention to capture a waveform in digitized form for subsequent digital processing with a resolution that is not achievable with prior art method of digitizing waveforms.
It is another object of the present invention to digitize a dynamic waveform with a resolution T.sub.w approaching T.sub.r.
It is yet another object of the present invention to digitize a dynamic waveform by providing sufficient time for sampling while achieving continuous digitizing of the waveform.